The present invention relates to a demodulator and a demodulating method suitable for a mobile phone such as a cellular phone. In particular, the present invention can simultaneously perform operation of improving the demodulation error rate caused by such as noise and external feedback loop operation being correction after detected, and can reduce the current consumption by restraining the increase of the process time at the simultaneous operation with an external correction circuit after detected, and can improve the CN ratio (ratio between carrier power and noise power).